Eyes
Components covered in this eye section:
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Orbit
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Eyeballs
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Muscles
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Neurovasculature
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Lacrimal Apparatus
Orbit
Components covered in this orbit subsection:
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Bones
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Foramina of the orbit
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Contents
Bones
7 bone form the orbit:
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Frontal bone
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Maxillary bone
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Zygomatic bone
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Lacrimal bone
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Ethmoid bone
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Palatine bone
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Sphenoid bone
Foramina
Foramina of the orbit:
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Optic canal
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Superior orbital fissure
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Inferior orbital fissure
Contents
Contents of the orbit:
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Intrinsic ocular muscles
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Extrinsic ocular muscles
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Ligaments supporting the eye
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Eyelids & eyeball
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The lacrimal (tear) apparatus
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Nerves & vasculature
Eyeball
Eyeball
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Outer fibrous layer
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Cornea (anterior- transparent part)
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Sclera (posterior- tough opaque part)
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Middle vascular layer/uvea
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Choroid
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Ciliary body (and ciliary processes)
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Iris
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Inner sensory layer
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Retina
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Optic non-visual part
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The eye is divided into:
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Aqueous humour- watery fluid in anterior segment
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Vitreous humour- gel in the posterior segment
Other structures to note:
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Lens
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Anterior chamber
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Posterior chamber
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Optic nerve
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Optic disc
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Central retinal artery
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Macula
Muscles
Components covered in this muscles subsection:
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Intrinsic muscles of the eye/Intraocular muscles (IOMs)
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Extrinsic muscles of the eye/Extraocular muscles (IOMs)
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Eye movements
IOMs
IOMs:
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Ciliaris- accomodation (for viewing objects at various distances)
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Constrictor pupillae- constricts pupil
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Dilator pupillae- dilates pupil
All have parasympathetic innervation from CN III (occulomotor nerve) except dilator pupillae (sympathetic innervation)
EOMs
EOMs:
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Levator palpebrae superioris
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Superior oblique
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Inferior oblique
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Superior rectus
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Inferior rectus
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Medial rectus
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Lateral rectus
All innervated by CN III (occulomotor nerve) except:
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Superior oblique- innervated by CN IV (trochlear nerve)
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Lateral rectus- innervated by CN VI (abducens nerve)
Eye Movements
Eye movements:
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Elevation
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Depression
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Abduction
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Adduction
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Intorsion
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Extorsion
Remember RADSIN (Recti ADuctors, Superiors INtortors)
EOMs:
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Levator palpebrae superioris (LPS)- elevate superior eyelid
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Superior oblique (SO)- abduction, intortion, depression
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Inferior oblique (IO)- abduction, extorsion, elevation
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Superior rectus (SR)- adduction, intorsion, elevation
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Inferior rectus (IR)- abduction, extorsion, depression
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Medial rectus (MR)- adduction
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Lateral rectus (LR)- abduction
Neurovasculature
Arteries
Arteries of the orbit and eye:
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Opthalmic artery (branch of ICA)- passes through optic canal
Veins
Veins of the orbit and eye:
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Opthalmic veins - passes through superior orbital fissure
Nerves
Nerves of the orbit and eye are cranial nerves:
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CN II (optic nerve)- passes through optic canal
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CN III (occulomotor nerve)- innervates ciliaris, constrictor pupillae, LPS, IO, SR, IR, MR (passes through supeiror orbital fissure)
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CN IV (trochlear nerve)- innervates SO (passes through supeiror orbital fissure)
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CN V1 (opthalmic nerve)- passes through superior orbital fissure
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CN VI (abducens nerve)- innervates LR (passes through supeiror orbital fissure)
Lymphatics
There are no lymphatics in the orbit.